Interest in the marine renewable energy devices, and particularly tidal stream turbines, has increased significantly over the past decade and several devices such as vertical and horizontal axis turbines and reciprocating hydrofoils are now being designed around the world to harness tidal stream energy. While tidal stream turbines are being developed at a high rate and getting closer to commercialisation, it is important to acquire the right tools to assist planners and environmentalists, not only in finding a right location for the turbines, but also in identifying their potential impacts on the surrounding marine and coastal environment. In this study, a widely used open source depth integrated 2D hydro-environmental model, namely DIVAST, was modified to simulate the hydro-environmental impacts of the turbines in the coastal environment. The model predictions showed very good agreement with previously published 1D model results. Then, for demonstration purposes, the model was applied to an arbitrary array of tidal stream turbines in the Severn Estuary and Bristol Channel which has the third highest tidal range in the world. The model has shown promising potential in investigating the impacts of the array on water levels, tidal currents and sediment and faecal bacteria levels as well as the generated tidal power, which facilitates investigating the relative far-field impacts of the arrays under various climate change scenarios or different formations of the array. (C) 2011 Elsevier Ltd. All rights reserved.